Conventionally, a scroll compressor in which each of a fixed scroll and an orbiting scroll has step portions provided at arbitrary positions in the spiral direction of the top surfaces and bottom surfaces of spiral wraps, and in which the spiral wraps having a higher wrap height on the outer circumferential side with respect to the step portions than on the inner circumferential side is known (for example, see PTL 1). Since the height of the compression chambers in the axial direction is higher on the outer circumferential side than on the inner circumferential side of the spiral wraps, this scroll compressor constitutes a scroll compressor capable of three-dimensional compression, i.e., compressing gas both in the circumferential direction and the height direction of the spiral wraps. Thus, a high-performance, compact, and light weight scroll compressor is achieved.
On the other hand, a scroll compressor has a pin-ring-type or Oldham's-ring-type rotation preventing mechanism for preventing rotation produced when the orbiting scroll is orbitally revolved. The rotation preventing mechanism, the fixed scroll, and the orbiting scroll inevitably have dimensional tolerances or assembly tolerances because they are components. Accordingly, it is difficult to completely prevent rotation of the orbiting scroll with the rotation preventing mechanism. Therefore, when the orbiting scroll receives a torsional moment in the orbital direction caused by a compression reaction force, a centrifugal force, or the like during operation, it inevitably rotates in a rocking (vibrating) manner by an amount corresponding to the above-mentioned tolerances. As a result, the spiral wrap of the orbiting scroll periodically comes into contact with and is separated from the spiral wrap of the fixed scroll, causing degradation in performance due to gas leakage and abnormal noise due to impacts.
To counter this, PTL 2 discloses a technique in which one or both of the ventral-surface side of the spiral wrap of the fixed scroll and the dorsal-surface side of the spiral wrap of the orbiting scroll are slightly cut. This reduces rocking (vibration) caused by the orbiting scroll coming into contact with and being separated from the spiral wrap of the fixed scroll when it receives a torsional moment in the orbital direction, and prevents degradation in performance due to gas leakage and abnormal noise due to impacts.
PTL 3 discloses a technique in which a pin on a housing side of a pin-ring-type rotation preventing mechanism is fixed at a position shifted in the direction opposite to the orbital direction by an amount corresponding to the tolerance and in which a knock pin for positioning a fixed scroll is disposed at a position satisfying positioning requirements determined such that, when an orbiting scroll is allowed to rotate in the orbital direction or the opposite direction, a gap between spiral wraps of the scrolls is a predetermined gap dimension. This prevents degradation in performance due to gas leakage and abnormal noise due to impacts.